Quick summary
Thymulin is a zinc-dependent nonapeptide hormone secreted by thymic epithelial cells that promotes T-cell differentiation and enhances cytotoxic activity. It is only biologically active when complexed with zinc, and circulating levels decline sharply with age and zinc deficiency.
Overview
Thymulin is a zinc-dependent nonapeptide hormone secreted by thymic epithelial cells, first characterized by Bach et al. in 1977. It is only biologically active when complexed with zinc. Thymulin plays a central role in T-cell maturation and immune modulation, with circulating levels declining sharply with age and zinc deficiency.
Mechanism of action
Thymulin binds receptors on immature thymocytes, mature T cells, and NK cells to promote T-cell differentiation and enhance cytotoxic activity. Its zinc-binding site (involving N-terminal pyroglutamate, Ser-4, Gln-5, and Ser-8) is required for receptor recognition. Thymulin stimulates IL-2 production, enhances NK cell killing capacity, and restores antibody avidity in aged or thymectomized animals. It modulates the Th1/Th2 cytokine balance and influences neuroendocrine-immune crosstalk.
Dosing protocols
| Purpose | Route | Dosage | Frequency | Notes |
|---|---|---|---|---|
| immune modulation (research) | subcutaneous | 10–50 mcg | daily or every other day |
Dosing information is for educational purposes only. Consult a qualified healthcare professional before using any peptide.
Research summary
Animal studies show thymulin restores immune function in aged rodents and thymectomized models, improving antibody production, skin graft rejection responses, and delayed-type hypersensitivity. Zinc supplementation can restore biological activity of circulating thymulin in zinc-deficient subjects. Human clinical trials are limited; most evidence remains preclinical. Research into thymulin gene therapy for pain modulation is ongoing.[1][2][3][4]
Evidence grading
Each claimed benefit is graded by the strength of available evidence. Grades reflect study quality, not effect size.
Strong = multiple RCTs · Moderate = limited trials or observational · Preliminary = animal or in vitro only · Insufficient = anecdotal or no published data
Side effects
Side effects vary by individual. This is not an exhaustive list. Report unusual symptoms to a healthcare professional.
Common stacks
Peptides commonly paired with Thymulin for synergistic effects.
Legal status
Thymulin is not FDA-approved for any indication. Available from research peptide suppliers. Not classified as a controlled substance.
Sourcing & access
Research compound
Thymulin is classified as a research compound. Regulatory status varies by jurisdiction. Always verify current legal status and source from vendors providing third-party certificates of analysis (COA).
Frequently asked questions
Thymulin (also known as Facteur Thymique Sérique or FTS) is a zinc-dependent nonapeptide hormone secreted by thymic epithelial cells, first characterized by Bach et al. in 1977. It is only biologically active when complexed with zinc, and circulating levels decline sharply with age and zinc deficiency — a decline closely tracking the functional involution of the thymus and age-related immune senescence.
Thymulin binds receptors on immature thymocytes, mature T cells, and NK cells to promote T-cell differentiation and enhance cytotoxic activity. Its zinc-binding site — involving N-terminal pyroglutamate, Ser-4, Gln-5, and Ser-8 — is required for receptor recognition. Thymulin stimulates IL-2 production, enhances NK cell killing capacity, restores antibody avidity in aged animals, and modulates the Th1/Th2 cytokine balance.
Thymulin's zinc-binding site is structurally required for receptor recognition and signal transduction — the peptide cannot bind its target receptors without zinc coordinated at specific positions. This explains why zinc deficiency produces a functional thymulin deficiency even when the peptide itself is present. Zinc supplementation in zinc-deficient subjects restores measurable thymulin biological activity, normalizing some immune parameters.
Thymulin is not FDA-approved for any clinical indication. It is available from research peptide suppliers and is not classified as a controlled substance. Most published evidence consists of animal studies showing restoration of immune function in aged rodents and thymectomized models. Human clinical trials are limited, and the compound is generally regarded as a research-stage peptide pending further clinical investigation.
Research references
- Thymulin (Zn-FTS): a zinc-dependent thymic hormone and T-cell differentiation factorPubMed
- Thymulin serum levels decrease with aging and zinc supplementation restores activityPubMed
- Thymulin analogue nonapeptide delivery and anti-inflammatory effectsPubMed
- Thymulin as an immune-restorative peptide in thymic insufficiency and agingPubMed